What is the correct procedure when mixing acid and water?

The correct procedure when mixing acid and water is to always add acid to water. This method is crucial for safety because when acid is added to water, the water absorbs the heat released by the reaction, reducing the risk of the acid splattering or boiling. The exothermic reaction generates heat, which can cause the liquid to expand and potentially splash if the acid is added to water.

Conversely, if water is poured into a concentrated acid, the heat generated can cause the mixture to boil violently, leading to hazardous situations. Therefore, following the correct procedure minimizes risks and enhances safety when handling corrosive substances in any water treatment or laboratory setting.